The invention relates to declogging processes for such filtering installations, as well as the installations using these processes.
Such dust-laden gases are frequently met with in the electrometallurgical industry and, according to the antipollution norms at present in force, these dust-laden gases must be filtered.
Such dust-laden gases are then filtered in filtration installations which comprise one or more filtering elements having an upstream face which is met by the dust-laden gas and a downstream face, the dust being deposited on said upstream face.
It is necessary to proceed periodically with cleaning of the filtering element(s) to remove the layer of dust deposited on the upstream face, this operation being called "declogging."
It is known to carry out this declogging operation by pneumatic means usually supplied with air.
Under these conditions, the mixture formed by the dust-laden gas (which has reducing properties) and air (which has oxidizing properties) may have explosive properties which present a considerable danger in view of the electrostatic phenomena which may occur at the moment of declogging.
In fact, a declogging operation which results in the loosening of the layer of dust (cake) deposited on the upstream face of each filtering element generates electrostatic charges capable of giving rise to electrostatic phenomena generating electric discharges.
It has already been proposed to carry out the declogging operation with an inert gas (for example nitrogen), but this increases operating costs.
It is an object of the invention to avoid the necessity of using an expensive inert gas.
The invention provides a declogging process and filtration installation whose operating cost is less than that of installations known at this time, while at the same time ensuring the same security against risk of explosion.